1. Field of the Invention
The present invention relates to a display module. More particularly, the present invention relates to a display module having a fingerprint sensor.
2. Description of Related Art
Fingerprint identification is an extensively applied biometric identification technology. To verify one's claimed identity, images of his or her fingerprints are first collected, and the fingerprint images are then measured and compared by means of identification software. Currently, various products are equipped with the function of fingerprint identification, such as notebook computers, cellular phones, portable hard drives, mobile phones, and so on. Since swirls on people's fingerprints are unique, the fingerprints can be characterized and used for authentication as a security mechanism. Moreover, the fingerprint identification technology can also be applied in an access control security system for identifying the user and validating access.
FIG. 1 is a schematic view illustrating light reflection when a liquid crystal display (LCD) panel is covered by a user's finger according to the pertinent art. Referring to FIG. 1, a conventional LCD panel 10 includes an active device array substrate 12, an opposite substrate 14, and a liquid crystal layer 16. The active device array substrate 12 includes a display unit 20 and a photosensor 30. When the LCD panel 10 is covered by a user's finger, the finger is irradiated by a backlight source L1 of a backlight module (not shown), and a light L2 is reflected by the finger to the photosensor 30 in the active device array substrate 12. Here, the reflected light L2 is absorbed by the photosensor 30 and thereby generates a photoelectric current. Next, the photoelectric current detected by an external integrator is converted into a voltage. Finally, an output voltage signal is converted in an analog-to-digital manner and undergoes appropriate image processing, such that fingerprint identification is completed.
Nonetheless, the conventional photosensor 30 is configured on the active device array substrate 12 in the LCD panel 10. Therefore, the light L2 reflected by the finger must pass through the opposite substrate 14, the liquid crystal layer 16, and the active device array substrate 12 and is then transmitted to the photosensor 30. Here, the reflected light L2 absorbed by the photosensor 30 is relatively reduced to a great extent after reflected or absorbed by several substrates. As such, the photoelectric current generated by the photosensor 30 is decreased, and the photosensor 30 is less capable of performing the function of identification due to the decreased photoelectric current.